WASHINGTON, Oct 5 (Reuters) - Washington entered the fifth day of a partial government shutdown on Saturday with no end in sight even as another, more serious conflict over raising the nation's borrowing authority started heating up.

The U.S. House of Representatives prepared for a Saturday session but with no expectations of progress on either the shutdown or a measure to raise the nation's $16.7 trillion debt ceiling. Congress must act by Oct. 17 in order to avoid a government debt default.

Republican House Speaker John Boehner tried on Friday to squelch reports that he would ease the way to a debt ceiling increase, stressing that Republicans would continue to insist on budget cuts as a condition of raising the borrowing authority.

On the shutdown, Boehner said Republicans were holding firm in their demand that in exchange for passing a bill to fund and reopen the government, President Barack Obama and his Democrats must agree to delay implementation of Obama's health care law.

The launch date for Obamacare health insurance exchanges came and went on Oct. 1, meaning Republicans are now in a more difficult political position of trying to stop something that has already begun.

Although essential government functions like national security and air traffic control continue, the economic and policy effects of the shutdown are amplified the longer hundreds of thousands of federal workers remain at home and unpaid.

Negotiations on tax and free trade treaties are on hold, enforcement of sanctions against Iran and Syria are being hindered, and a government tester of dangerous consumer products spends his days at home.

"Do not mistake this momentary episode in American politics as anything more than a moment of politics," U.S. Secretary of State John Kerry told reporters at an Asia-Pacific leaders conference in Bali, Indonesia, on Saturday.

"Nothing will diminish our commitment to Asia...we will continue to fulfill our responsibilities and our engagement around the world," said Kerry, who is standing in for Obama after the president cancel his Asian trip.

TEMPERS FRAY

Nerves and sometimes tempers frayed on Friday after several weeks of long sessions of Congress and non-stop posturing.

"This isn't some damn game," said Boehner, responding to a Wall Street Journal article that quoted an unidentified White House official saying Democrats were "winning" the shutdown battle.

The Democratic president reiterated that he was willing to negotiate with Republicans, but said, "We can't do it with a gun held to the head of the American people."

"There's no winning when families don't have certainty over whether they're going to get paid or not," Obama told reporters when he visited a downtown Washington lunch spot that was offering a discount to furloughed federal government workers.

The shutdown began on Tuesday when the Republican-led House of Representatives refused to approve a bill funding the government unless it included measures designed to delay or defund key provisions of Obama's signature legislation, the 2010 Affordable Care Act, which are now being implemented.

Obama again appealed to Boehner to bring a "clean" funding bill - without reference to the health reforms - to a vote in the House, where many Democrats believe it could pass with a combination of Democrats and a few of the majority Republicans.

POSSIBLE MANEUVER

Democratic leaders in the House said on Friday they were working on a maneuver that, if successful, would force a vote on legislation to fully reopen the federal government.

The plan involves a rarely used "discharge petition" that would dislodge an existing bill from a committee and send it to the House floor if a simple majority of lawmakers in the chamber sign the petition.

Such a move would take a week or so to clear procedural hurdles in the House, according to Democratic U.S. Representative George Miller. A House vote might not come until at least Oct. 14, which is a federal holiday, said Miller from California.

Democratic Representative Louise Slaughter of New York called on 22 moderate House Republicans to put their "voting cards where your mouths are" and help end the shutdown.

Slaughter said that although the 22 have declared support for an unconditional bill to fund the government, they have sided with their own Republican leaders and the conservative Tea Party wing in repeatedly opposing Democratic efforts to bring such a Senate bill up for a House vote.

"When the opportunity arose, courage failed them," Slaughter said in a House speech.

The government was obliged to close many of its operations because Congress failed to pass a spending bill by Oct. 1, the start of the new fiscal year.

Facing public anger over the government shutdown, the House has adopted a strategy of voting piecemeal to fund some popular federal agencies - like the Veterans Administration, the National Park Service and the National Institutes of Health - that are partially closed.

Republicans know that neither the Democratic-controlled Senate nor Obama will agree to that approach, but it allows them to accuse Democrats of working against the interests of veterans, national parks and cancer patients.

"PIECEMEAL" FUNDING BILLS

House Republicans have been working through nearly a dozen bills to fund targeted programs. They included: nutrition programs for low-income women and their children; a program to secure nuclear weapons and non-proliferation; intelligence gathering; border patrols; weather monitoring; Head Start school programs for the poor. With a major storm approaching the Gulf coast, one of the measures passed by the House on Friday would fund federal disaster assistance.

The Democratic-controlled Senate says it will reject the piecemeal funding measures and Obama has said he would veto them. One measure the White House does support is a bill to retroactively pay federal workers once the government reopens, likely to pass the House on Saturday.

Global stocks posted a loss for the week while the dollar hovered near an eight-month low on investor fears the budget standoff in Washington will drag on until politicians reach a deal to raise the U.S. debt ceiling.

The shutdown and the possible failure to raise the debt ceiling, have prompted a number of warnings from big business.

AT&T Chief Executive Randall Stephenson, addressing a possible default, said in a statement, "It would be the height of irresponsibility for any public official to consider such a course. In fact, even the discussion of default poses great risk to our economy and to our country."

The government's September employment report, the most widely watched economic data both on Wall Street and Main Street, had been scheduled for release on Friday but was a casualty of the shutdown.